1. Field of the Invention
The present invention relates generally to removing liquid from substrates, and more particularly to apparatus and methods for drying batches of substrates that have been wet in a liquid bath, after which the batches of substrates and the bath are separated at a controlled rate to form a thin layer of liquid on each substrate of the batches as the batches of substrates are positioned in a gas-filled volume, wherein the volume is defined by an elongated hot chamber that continuously transfers thermal energy to the batches of substrates in the volume, and wherein curtains of hot gas directed into the volume and across the batches of substrates and out of the volume continuously transfer thermal energy to the batches of substrates, so that the thermal energy transferred to the batches of substrates in the volume evaporates the thin layer from each of the substrates without decreasing the rate of separation of the batches of substrates and the bath below a maximum rate of such separation at which a meniscus will form between the bath and the surface of each substrate during such separation.
2. Description of the Related Art
In the manufacture of semiconductor devices, process chambers are interfaced to permit transfer of substrates (such as semiconductor wafers of any of various sizes) between the interfaced chambers. Such transfer is via transport modules that move the substrates, for example, through slots or ports that are provided in the adjacent walls of the interfaced chambers. For example, transport modules are generally used in conjunction with a variety of substrate processing modules, which may include semiconductor etching systems, material deposition systems, flat panel display etching systems, and substrate cleaning systems. Due to growing demands for cleanliness and high processing precision, there has been a greater need to reduce the amount of human interaction during, between, and after such processing steps. This need has been partially met with the implementation of vacuum transport modules which operate as an intermediate substrate handling apparatus (typically maintained at a reduced pressure, e.g., vacuum conditions). By way of example, a vacuum transport module may be physically located between one or more clean room storage facilities where substrates are stored, and multiple substrate processing modules where the substrate are actually processed, e.g., etched or have deposition performed thereon, or cleaned. In this manner, when a substrate is required for processing, a robot arm located within the transport module may be employed to retrieve a selected substrate from storage and place it into one of the multiple processing modules.
Despite use of such intermediate substrate handling apparatus, it is still necessary to clean and dry the substrate at the completion of such processing. As an example, after the substrate have been cleaned, the substrate may have a non-uniform coating of liquid. A substrate with such non-uniform coating of liquid, or with one or more drops of liquid thereon, or with any liquid thereon in any physical form, may be said to be xe2x80x9cwetxe2x80x9d. In contrast, a substrate having a uniform coating of liquid may be said to be xe2x80x9cuniformly wetxe2x80x9d.
In the past, substrates such as annular-shaped disks of many various sizes have been used for manufacturing data storage devices, for example. Such substrates have also been subjected to a drying operation. After cleaning and while wet, such substrates have been placed in a tank containing a bath of hot liquid. In one type of drying operation, the hot liquid has been drained from the tank at a rate such that a thin layer of liquid, rather than one or more drops of liquid, forms on that portion of such substrate that is out of the draining liquid. The thin layer has been preferred over one or more drops because a drop of liquid has a high volume, e.g., from about 0.001 ml. to about 0.020 ml. In comparison to the drop, a thin layer of liquid on a substrate such as a 95 mm diameter disk, may only have a volume of at the maximum diameter of the disk of about 0.0007 ml, for example. Evaporation of a drop generally results in the concentration of small particles at the last small point on the disk at which the drop exists. When the substrate is a wafer, such concentration may result in defects in a chip made from the wafer.
To remove the thin layer from such substrate, reliance has been placed on the thermal energy stored in such substrate to provide the thermal energy necessary to evaporate the thin layer. However, when such substrate is a xe2x80x9cwaferxe2x80x9d, as defined above, problems have been experienced in not properly drying the thin layer from the wafer. For example, it appears that using only such stored thermal energy, the thin layer evaporates from the wafer at a rate less than the maximum rate of separation of the liquid bath and the wafer at which a meniscus will form between the liquid bath and the surface of the wafer during such separation. Thus, the rate at which the liquid is drained from the tank has to be decreased to match the rate of evaporation. Alternatively, the wafer would have to be retained in the tank after the draining has been completed. Each of such decreased rate of draining and such retaining increases the time required to dry the wafer, which increases the cost of fabricating devices based on the wafer.
Additionally, when the substrate is a disk that is used to manufacture generally low-cost data storage devices, for example, it is necessary to process large numbers of such substrates at the same time. However, difficulties have been experienced in assuring uniform drying of each of such substrates. As an example, if the flow rate of the hot gas into the volume is increased in an attempt to process a large number of substrates, the higher flow rate gas may disturb the surface of the liquid bath, resulting in splashing of the liquid onto the surfaces of the substrates. Such splashing may form drops on one or more of the surfaces. Also, even when more than one substrate is processed at the same time, use of a uniform rate of movement of the substrates into, within, and out of the liquid result in inefficiencies, such as relatively long periods of time of a drying cycle. In addition, when more than one substrate is processed at the same time relative humidity problems within the gas volume affect processing of more than one substrate at a time.
In view of the forgoing, what is needed is apparatus and methods of efficiently drying substrates. Such efficient drying should allow batches of the substrates to be efficiently processed. Such efficient drying should also allow the rate of movement of the batches of the substrates to be controlled according to the nature of the movement, e.g., entry of the substrates into the liquid, or movement of the substrates from a deep immersion position to a shallow immersion position in the liquid, or suspense of movement of the substrates, for example. Such control should also allow the liquid and the substrates to be separated at a rate no less than the maximum rate of separation of the liquid and the substrates at which a meniscus will form between the liquid bath and the surface of the substrate. In addition, the efficient drying should assure that the upper surface of the liquid is smooth during such separation. Further, the efficient drying should minimize the effect of relative humidity on the drying of batches of the substrates. Also, the efficient drying should very rapidly remove from the substrate a thin layer of liquid that forms on the substrate as the substrate and the bath are separated, wherein xe2x80x9crapidlyxe2x80x9d means such removal occurs before the substrate and the bath have been completely separated e.g., separated by 0.004 inches, for example.
Broadly speaking, the present invention fills these needs by providing apparatus and methods of efficiently removing fluid from batches of substrates. The efficient removing is attained by providing apparatus and methods for drying batches of substrates that have been uniformly wet in a fluid bath. Such efficient drying is enhanced by controlling the rate of movement of the batches of the substrates according to the nature of the movement, e.g., entry of the substrates into the liquid, or movement of the substrates from the deep immersion position to a shallow immersion position in the liquid, or suspense of movement of the substrates, for example. As another example, the batches of substrates and the bath are separated at a controlled rate to form a thin layer of fluid on each of the substrates in the batches as each of the substrates is positioned in an elongated gas-filled volume. In addition to such separation, the efficient removing is attained by defining the gas-filled volume by use of an elongated hot chamber and curved gas inlet manifolds that form an elongated curtain of hot gas that transfers thermal energy to the batch of substrates in the volume. Further, during a drying cycle, the elongated curtain of hot gas is continuously directed into the volume and across each substrate of the batch of substrates and out of the volume to continuously transfer thermal energy to the wafer. While the directing of the gas out of the volume is independent of the separation of the bath and the substrates, the rate of gas flow into the volume is decreased during entry of the batches of the substrates into the volume. In addition, conditions are controlled so that the upper surface of the fluid is smooth during such separation. The thermal energy transferred to the batches of substrates in the bath and in the volume very rapidly evaporates the thin layer from the wafer without decreasing the rate of separation of the batches of substrates and the bath below the maximum rate of such separation at which a meniscus will form between the bath and the surface of the substrates during such separation. The effect of relative humidity in promoting recondensation of liquid vapor onto the dried substrates of the batches is avoided by providing an exhaust fan to draw the liquid vapor-laden gas from the volume at a location away from the elongated hot chamber.
Such efficient removal enables the substrate throughput of such apparatus and method to be limited only by the type of substrate that is being dried, and the type of liquid used to wet the substrate. For example, the characteristics of particular types of substrates and liquid dictate the maximum rate of such separation of the substrate and the bath at which a meniscus will form between the bath and the surface of the substrate during such separation, and at which the substrate will be uniformly wet.
In one embodiment of the present invention, a system for drying batches of substrates is provided with an elongated bath enclosure configured to hold fluid. The fluid defines a top fluid surface and the elongated bath enclosure has an upper end defined by a weir having a saw-toothed configuration. A temperature and humidity-controlled chamber is defined above the upper end, the chamber being elongated corresponding to the elongation of the elongated bath and having opposing long walls. The chamber has a series of first openings along the long walls at a first location adjacent to the upper end and opposed second openings at a second location that is spaced from the upper end.
In one aspect of the one embodiment of the present invention, a system for drying batches of substrates is provided for substrates having opposite planar sides that are parallel to a planar axis. A substrate transport unit immerses a plurality of batches of substrates in the fluid with the planar axis of each substrate generally perpendicular to the fluid surface and the opposite planar sides of each substrate generally perpendicular to the long walls. A drive is provided for causing the substrate transport unit to move the batches of substrates within and out of the fluid with the planar axis remaining generally perpendicular to the fluid surface. The drive controls the rate of movement of the batches of substrates according to the location of the batches of substrates within and out of the fluid.
In another aspect of the one embodiment of the present invention, a controller is provided to control operation of the drive to simultaneously move the batches of substrates at rates of movement controlled according to the location of the batches of substrates within and out of the fluid.
In a next embodiment of the present invention, apparatus is provided for drying a plurality of batches of substrates, wherein each of the substrates has opposite sides. A bath is adapted to contain hot liquid, and the liquid defines an upper liquid surface. The bath is elongated to simultaneously receive the plurality of batches of substrates aligned in series along a batch substrate path. The bath has a saw toothed weir defining an upper end of the bath over which the liquid may flow out of the bath. A liquid collection tank surrounds and supports the bath for receiving the liquid flowing over the weir, and the tank has an upper end above the weir. A drain system is connected to the tank for recirculating the liquid that flowed over the weir. The drain system heats, filters, and returns the liquid to the bath. An enclosure is configured to receive the plurality of batches of substrates aligned in series along the batch substrate path. The enclosure has opposing elongated walls positioned on opposite sides of the batch substrate path. Also, the enclosure has an upper end and a base spaced from the upper end, the walls being connected to the tank for supporting the tank and the bath. A series of gas inlets is defined in each of the opposing elongated walls at the upper end of the enclosure and spaced from the weir. The inlets extend along the opposing elongated walls on opposite sides of an upper position of the batch substrate path. A gas outlet adjacent to the base of each of the elongated walls is spaced from the upper liquid surface. The enclosure and the inlets and the outlets define continuous gas flow paths from the inlets through the enclosure to the outlets, the flow path extending across the weir for drawing ambient vapor from the bath directly to the outlets.
In another aspect of the next embodiment of the present invention, the substrates each have a narrow edge between the sides and the carrier has elongated spaced arms configured to extend in the enclosure parallel to and between the opposing elongated walls. A substrate batch nest corresponds to each batch of the substrates. Each nest includes a plurality of spaced bars and spaced end plates mounting the bars on the spaced arms. Each of the bars includes a vertical surface intersecting a three-dimensional V-shaped notch that corresponds to each substrate to be carried. Each V-shaped notch is formed in the bar with a valley and opposite walls extending at an acute angle with respect to the vertical surface. The vertical surface and the acute angle of the V-shaped notch combine to limit the contact between the substrate and each V-shaped notch. The contact is a substantially point contact between one of the opposite walls of the notch and one end of the narrow edge of the substrate.
In a further embodiment of the present invention, apparatus is provided for drying a plurality of batches of substrates. There is a relatively short wall at each end of the opposing elongated walls. The upper end of the enclosure is provided with an elongated opening defined by the opposing elongated walls and by the relatively short walls. The elongated opening is configured to receive the plurality of batches of substrates aligned in the series along the batch substrate path. A plurality of doors is provided, each door having first ends adjacent to one of the short walls and opposite second ends adjacent to the other of the short ends. Door mounts are adjacent to each of the short walls for guiding the doors across the elongated opening in opposition to each other. A drive is mounted adjacent to one of the short walls and connected to the first end of one of the doors. A first endless belt is driven by the drive and is connected to the corresponding first end of the other of the doors so that the corresponding first ends of the doors move simultaneously on the door mounts. A connecting shaft is provided for each of the doors. The shafts are driven by the first endless belt and extend from the one of the short walls to the other of the short walls. A second endless belt driven by the connecting shafts moves the opposite corresponding second ends of the doors simultaneously and in synchronism with the movement of the corresponding first ends of the doors to open or close the elongated opening.
In a method embodiment of the present invention, drying a substrate includes an operation of simultaneously immersing a plurality of batches of substrates into a bath of hot liquid having a given depth extending from a liquid surface to a bottom of the bath. The immersing operation positions the batches of substrates at a deep immersion location adjacent to the bottom. The substrates are retained at the deep immersion location for a predetermined period of time. After the predetermined period of time, there is an operation of quickly transiting the batches of substrates from the deep immersion location to a shallow immersion location adjacent to the liquid surface. A further operation pulls the batches of substrates out of the liquid from the shallow immersion location to dry the batches of substrates.